Background art will be described by taking an absorption heat pump device as an example. This device comprises a condenser for condensing water vapor to form liquid phase water, an evaporator for evaporating the liquid phase water formed in the condenser to form water vapor, an absorber for causing a highly viscous absorbing liquid to absorb the water vapor evaporated in the evaporator and diluting the absorbing liquid to form a diluted absorbing liquid, and a regenerator for concentrating the absorbing liquid by evaporating water contained in the diluted absorbing water formed in the absorber in the form of water vapor.
According to the abovementioned absorber, technique has been developed for causing the absorbing liquid to absorb the water vapor evaporated in the evaporator and diluting the absorbing liquid to form a diluted absorbing liquid. The absorbing liquid before absorbing the water vapor has a high viscosity and can be regarded as a tenacious material (a viscous substance). Therefore, the absorbing liquid before absorbing the water vapor tends to form a mass and hardly spreads, and therefore has a limit in absorbing the water vapor. Hence, dilution efficiency has not been sufficient.
Conventionally known as an example of the abovementioned absorber is an absorber in which a plurality of grooves are arranged in parallel on outer surfaces of heat transfer pipes in a longitudinal direction of the heat transfer pipes and fine concaves and convexes of oxide films are formed on the outer surfaces of the heat transfer pipes by applying oxidation treatment by heating the heat transfer pipes in the air (Patent Document 1). This document describes that this absorber improves in wettability at the outer surfaces of the heat transfer pipes, facilitates spreading of an absorbing liquid having a high viscosity along the outer surfaces of the heat transfer pipes and can enhance the absorbing ability that an absorbing liquid absorbs water vapor.
Moreover, known as an evaporator used in an absorption heat pump device is an evaporator with a system in which a dilute ammonia solution is atomized by a spray nozzle and introduced into heat transfer pipes (Patent Document 2). Furthermore, known as a liquid spray device of an absorption water cooler/heater is a device which causes a spray solution to flow out from tray holes of a bottom wall of a tray and drop down on heat transfer pipes of a heat exchanger (Patent Document 3).    Patent Document 1: Japanese Unexamined Patent Publication No. H10-185356    Patent Document 2: Japanese Unexamined Patent Publication No. 2001-165528    Patent Document 3: Japanese Unexamined Patent Publication No. 2000-179989